With a recent growing demand for a high integration density, various direct type of connectors have been developed as low insertion force types. In general, such a low insertion type connector has a plurality of spring contacts arranged in a socket-formation having of an insulating material with their contact points projected in an insertion inlet into which a printed circuit called a daughter board is inserted. These contact points are arranged as two contact point arrays along the longitudinal direction of the insertion inlet and a gap is created between these contact arrays to receive the edge portion of the printed circuit board. The respective contact point arrays are arranged, in an offset way, in a depth direction of the insertion inlet, that is, in the insertion direction of the printed board. When, on the other hand, the printed circuit board is to be connected, on one surface side of the edge portion the corresponding contact point array is contacted with an area near the forward end of the edge portion of the printed circuit board, while on the other surface side of the printed circuit board the corresponding contact point array is contacted with an area somewhat distant from the forward end of the edge portion of the printed circuit board.
When the edge portion of the printed circuit board is inserted between the contact point arrays and the printed circuit board is swung in a direction in which these contact point arrays are separated from each other, the contact points of the respective spring contacts are displaced and, by a spring force trying to return the contact points back to an initial position, the respective contact points are positively made in contact with corresponding conductors arrayed at the edge portion of the printed circuit board.
In order to positively fix the printed circuit board while holding the respective spring contacts in a better contacting state, a latching mechanism is provided so that the printed circuit board is held in the swung position and fixed to a housing. Various types of latching mechanisms have been developed as such.
The latching mechanism as disclosed, for example, in U.S. Pat. No. 4,986,765 is equipped with a leaf-spring-like latch member formed of a metal sheet and the printed circuit is latched by the metal latch member. The metal latch member has an elastic section in a recess of the housing base, a metal section projected downwardly from the elastic section and inserted into a through bore in the housing base, and a latch section provided above the elastic section. When the printed circuit board is swung, the latch section engages the edge portion of the printed circuit board to externally urge the elastic section and a cutout fitted over the side edge of the printed circuit board so that the printed circuit board is held in a predetermined swung position.
U.S. Pat. No. 5,161,995 discloses a latching mechanism equipped with a leaf-spring-like latch member formed of a metal sheet. The latch member comprises a mount section situated below the elastic section and latch section situated on the upper side. The mount section has one pair of U-shaped mount arms fixedly wound around a support pole situated near the insertion inlet of the printed circuit board. These mount arms support the reaction force of that spring. Further, the latch section provides a guide face for, upon the swinging of the printed circuit board, engaging with the edge portion of the printed circuit board to outwardly urge the elastic section and an engaging wall for engaging with one face of the printed circuit board to prevent return motion of the printed circuit board.
In either of these latching mechanisms, it is possible to readily latch and unlatch the printed circuit board through the utilization of the characteristic of the metal leaf spring. However, any of the aforementioned latch mechanisms leaves room for improvement in view of the latch members being formed of a metal sheet.
Since, upon the mounting of the printed circuit board, the printed circuit board is swung slidably along the guide sections or guide faces of the latch members to cause the latch members to be bent against their elastic force, there is a risk that a coating layer of the printed circuit board or insulating substrate will be damaged due to the contacting or slide motion of the printed circuit board. In particular, where the printed circuit board per se becomes larger due to the high integration density of the printed circuit board or the number of spring contacts is increased, a greater total force by the spring contacts is required. If the latch member is made correspondingly great in size, a greater force is required to bend the latch member. As a result, there is a greater possibility that the printed circuit board will be damaged.
Further, it is desirable to prevent a metal member other than the contacts, such as a metal member near the insertion inlet of the printed circuit board in particular, from being exposed as much as possible.
It is accordingly the object of the present invention to provide a socket for a printed circuit board which can readily and positively attach and detach the printed circuit board without any associated metal member or members being exposed and can do so even if a greater number of spring contacts are used.